One plant has slightly yellow tips

[growlo_b]

Hey all,

I have 4 plants in late veg and one started showing slight yellowing in the tips a couple of days ago. The yellowing really hasn’t really progressed at all since I discovered it but I’m still wondering what it could be. It’s odd because all other plants are pristine.

I first thought it could be nute burn but after measuring runoff ec, I actually found it to be slightly lower than the feed ec. The feeding is about 1100 and runoff is a little less than 1000. That’s right on track based on the Coco for Cannabis feed schedule I’m following.

I then thought it could be light stress but the lights are a couple of inches above manufacturer recommended height.

The yellowing is just in the tips and mostly in the newer leaves.

Any ideas? See the picture for details.

Grow Details:

- Coco
- General Hydroponics nutes
- LED lights (Mars Hydro SP250) at 20” currently
- Day temp: 75*
- Night temp: 69*
- RH: 60-65%

 

[Anthem]

you are getting nutrient burn. Most of the nutrient companies base their ppm's on the plant being under a 1000 watt de Hps. use just water and cal mag for 2 waterings. try backing them off about 300 ppm for one feed and then start going up by about 100 ppm a feed until you see the tips yellowing again and back off about 200 ppm.

 

[growlo_b]

you are getting nutrient burn. Most of the nutrient companies base their ppm's on the plant being under a 1000 watt de Hps. use just water and cal mag for 2 waterings. try backing them off about 300 ppm for one feed and then start going up by about 100 ppm a feed until you see the tips yellowing again and back off about 200 ppm.

Thanks, so should I do this for just this plant or all 4 plants? The rest show no signs.

 

[Anthem]

Thanks, so should I do this for just this plant or all 4 plants? The rest show no signs.

I would back the nutrients down on the balance of the plants like 200 ppm and continue moving those plants forward. But bear in mind the one plant with the tip burn will be slightly behind the rest in height and fullness.

 

[Vagician]

I agree that it's nutrient burn. It looks like you have early iron deficiency (new growth is yellow between leaf veins) from too high of a nitrogen content (burnt tips curling down). What Anthem is suggesting sounds like the best approach to the problem. Your temp/RH look good, what is your pH? A little side note; GH has been busted many times for not actually having the concentrations stated on their nutrient bottles whether too high or too low. I'm not sure what is available in your area, but see if you can move toward something more natural like fish emulsion and soil amendments instead of GH salt nutrients. A lot of people say it is too complicated to switch, but if you can successfully grow with GH then anything else is easy.

 

[growlo_b]

Your temp/RH look good, what is your pH?

I've been feeding between 5.9 and 6.1 for PH. I'll grab a runoff PH tonight. I don't know why I didn't test that yesterday.

A little side note; GH has been busted many times for not actually having the concentrations stated on their nutrient bottles whether too high or too low.

Yeah, I've definitely heard that. That's why I opted to use the Coco for Cannabis feed chart which was custom-tailored to GH nutes and has served me well for 3/4 plants thus far. I've been obsessive over PH and EC but I know things can get out of range pretty easily with GH nutes.

I am interested in trying organic, amended Coco for the next grow. It would solve a bunch of problems for me including the pain of drain-to-waste and insane watering/feeding requirements.

 

[growlo_b]

So, I went through two feedings of cal mag water, then did a low ppm feed last night. The plant looks good. Leaf tips are still yellow but it’s grown a lot and looks good.

If the leaf tips are just yellow and not browned or dried out, should they recover or are they yellow forever?

 

[growlo_b]

Update: Lead tips are getting their green back and the plant is exploding. Thanks for the help team!